The present invention provides insulation material for ensuring insulation between the core and the conductor coil of an electrical machine. A rotary electrical machine, such as an electrical motor, an electrical generator, or the like, has a core with a plurality of teeth. The conductor coil is placed in slots located between the teeth in the core. A slot liner is a sheet of insulation material placed between the core and the conductor coil. The slot liner provides electrical insulation between the core and the conductor coil.
Insulation material in rotary electrical machines used in high temperature-environments must provide adequate heat resistance. Mica is typically used in this type of insulation material. Mica insulation material has pieces of aggregate mica or peeled mica which are attached together. Aggregate mica is mica formed in fine flakes which are hardened with resin. Peeled mica is mica formed in thin pieces that are peeled from a mica stone.
The heat resistance of the resin which binds the small pieces of mica in aggregate mica insulation may be inadequate. Furthermore, aggregate mica insulation is brittle, and therefore, holes may form in the insulation material during manufacturing or by vibrations and the like that occur while using rotary electrical machines. These holes can damage the insulation material. Additionally, peeled mica insulation is not flexible and may break as it is placed inside the slots, thereby damaging the insulation material. Peeled mica insulation is also expensive.
Sheets of mica insulation material are typically not pliant. When forming the portion of the conductor coil that protrudes from the end of the core, the insulation material supports a load that may break the insulation material. To minimize the risk of breaking the mica insulation material, a conventional slot liner can be constructed by layering the mica insulation material with a layer of reinforcement material, such as resin, having relatively good mechanical strength.
The layer of reinforcement resin in the conventional slot liner described above is interposed between the conductor coil and the core. However, the resin may expand or deform due to high temperatures, which can result in the separation of the reinforcement layer from the core. The separation of the reinforcement layer from the core prevents the transfer of heat generated from the conductor coil, thereby weakening the ability of the conductor coil to transfer heat to the core.